我有一个查询来查找看起来像这样的废弃购物车：
SELECT c.customerid,
c.custconfirstname,
c.custconemail,
o.ordstatus,
o.orddate,
GROUP_CONCAT( 'Order Id: ', orderid, ' | Product name: ', ordprodname, ' | Quantity: ', ordprodqty, '<br>' ) AS ordered_items
FROM isc_customers c
LEFT OUTER JOIN isc_orders o ON o.ordcustid = c.customerid
LEFT OUTER JOIN isc_order_products op ON op.orderorderid = o.orderid
LEFT OUTER JOIN isc_product_images pi ON pi.imageprodid = op.orderprodid
GROUP BY c.customerid
HAVING COUNT( DISTINCT o.ordcustid ) >0
AND o.ordstatus = 0
AND o.orddate < UNIX_TIMESTAMP( ) - '18000'
AND o.orddate > UNIX_TIMESTAMP( ) - '259200'
对于每个客户（唯一的customerid）BLOB将为ordered_items生成类似的内容：
Order Id: 15256 | Product name: PROD A | Quantity: 1
,Order Id: 15256 | Product name: PROD B | Quantity: 1
,Order Id: 15299 | Product name: PROD A | Quantity: 1
,Order Id: 15301 | Product name: PROD A | Quantity: 1
这基本上可以解释为客户在时间范围内有3辆废弃的推车。因为此查询将用于发送已弃用的购物车电子邮件，所以我不希望发送垃圾邮件并发送电子邮件，其中包含来自每个废弃购物车（唯一订单）的每件商品，原因有多种，包括上述示例中的客户已尝试过通过3个订单将产品A放入购物车3次，从而在电子邮件中获得3次商品。
那么如何限制查询以便它只返回每个customerid 1个orderid的结果？